The invention relates to a coupling device for the sealed coupling of first and second pipe sections which are movable one relative to the other.
Coupling devices are known in which both pipe sections are provided at their mutually adjacent ends with coupling flanges, which can be connected one to another by fastening means and between which a seal is disposed so as to obtain a mutual sealing of the two pipe sections. A satisfactory seal can only be achieved if the two flanges are clamped together fixedly with considerable force. Moreover, even small deviations of the flanges from a mutually parallel arrangement are sufficient to cause the media carried in the pipe sections (gases or liquids) to leak out.
In order to prevent this problem, it is known from U.S. Pat. No. 3,761,114 to dispose in an annular groove in one of the flanges a seal which, in the annular groove, has a double-walled portion, the walls of which at the groove floor are connected one to another in such a way that the space between the walls of the seal is subjected to the pressure of the medium in the pipe sections. In this way, the seal becomes pressed against the faces to be mutually sealed, which pressing becomes greater with rising pressure. It is here necessary, however, that the faces of the flanges bear precisely one against the other and that the pressure of the medium is large enough to ensure the pressing of the seal. Furthermore, additional fastening means are necessary to fasten the flanges one against the other.
From U.S. Pat. No. 3,642,289 a similar arrangement is known, in which, in the annular groove of a flange, an annular piston is movable, which on its internal and external peripheral faces and its outer end face has sealing elements for sealing against the walls of the annular groove and against the other flange. The space between the floor of the annular groove and the piston is subjected to a pressurized medium so as to press the piston against the other flange. The piston must be guided relatively precisely in the annular groove, since otherwise the sealing against the annular groove is lost. Here too, therefore, the flanges must be relatively precisely parallel to each other in order to obtain a satisfactory seal.
In dishwashers with radial offset between the pipe sections which are to be coupled together, it is further known from DE 199 26 962 to fasten a bellows seal to one flange, while the other flange, at least in a radial direction, is configured with a relatively large surface area in order to guarantee a bearing contact of the bellows seal if the two pipe sections are radially displaced. The pressing of the bellows seal against the movable flange is in this case realized by purely mechanical means.